The adjoint equations for the control system (REF )-() are ([1]}):
\(\lambda _f ^{\prime }(t) &=& -f_x^T(x(t), z(t), u(t)) \lambda _f(t) - g_x^T(x(t))\lambda _g(t),  \\0 &=& - f_z^T(x(t), z(t), u(t)) \lambda _f(t). \) 
